IDWeek: Flu vaccine reduces risk of hospitalization and death

Two analyses supported by the Centers for Disease Control and Prevention’s (CDC; GA, USA) US influenza data have demonstrated that immunization reduces the risk of hospitalization in children and death in adults.

The studies were both presented at IDWeek (2–6 October 2019, Washington, DC, USA).

The first study assessed the benefits of flu vaccination in 3600 children aged between 6 months and 7 years old across seven pediatric medical centers. All children were hospitalized with an acute respiratory illness over two seasons, and patients were then tested for to confirm an influenza diagnosis.

The team then compared the frequency of flu vaccination among children who tested positive for flu against vaccination rates among children with illnesses other than flu, discovering that children receiving the vaccine were half as likely to be hospitalized with flu when compared with those who weren’t vaccinated (49% for the first season, 51% for the second).

The second study investigated 43,608 adults with laboratory-confirmed flu over five seasons. The researchers assessed vaccination status among hospitalized patients to determine the reduction in the likelihood of severe outcomes among vaccinated patients, when compared with unvaccinated patients.

The results suggested that vaccination reduced the risk of severe outcomes – for example death, pneumonia, admission to intensive care and mechanical ventilation – by over one-third. Specifically, the risk of death was reduced by 36%, and the risk of pneumonia was reduced by 17%. Vaccination was also associated with shorter stays in intensive care.

Lead author of the study in adults, Shikha Garg (CDC), commented: “While flu vaccines vary in how well they work and some people who get vaccinated still get sick, this study provides more evidence that getting vaccinated can reduce the severity of the illness. This type of research helps us more fully understand the benefits of vaccination.”

Angela Campbell (CDC), lead author of the pediatric study, concluded: “These studies add to the evidence that influenza vaccines prevent serious complications from flu. They show just how important it is that everyone 6 months and older who is eligible to get a flu vaccine does so every year.”

How is the flu vaccine made?

There are thee production methods approved by the US FDA for manufacturing flu vaccines; egg-based, cell-based and recombinant. The most common method to make flu vaccines is using an egg-based manufacturing process, which has been used for over 70 years.

How are the strains in the flu vaccine determined?

Twice a year, the WHO organizes a consultation with the Directors of the WHO Collaborating Centers. Scientists at each of the five main centers have spent time gathering and analyzing the data together to identify new flu strains and to determine which strains of the virus are most likely to spread and cause illness in the upcoming flu season. These meetings take place in February for the Northern Hemisphere’s vaccine and in September for the Southern Hemisphere’s vaccine. Following the meeting the WHO recommends specific vaccine viruses for inclusion in influenza vaccines, but then each country makes their own decision about the viruses that should be included in influenza vaccines licensed in their country.